This invention relates generally to fractionation of air by selective adsorption, and particularly to apparatus and processes using gas permeable membranes and adsorbent materials for increasing the concentration of oxygen of atmospheric air and decreasing the concentration of nitrogen.
Patients suffering from respiratory ailments such as emphysema and pneumonia, which severely restrict the patient's lung capacity, are commonly provided with a source of oxygen-enriched air.
A common source for enriched oxygen is a metal cylinder containing oxygen under a high pressure. The oxygen is supplied through suitable tubing and pressure regulators to the patient. The cylinders are heavy and cumbersome and present a danger of fire and explosion. Additionally, relying on oxygen cylinders requires that the user have enough oxygen in the cylindrs to last the time between available refillings. The oxygen cylinders are also quite limited in the amount of oxygen they can hold. This requires either maintaining a large supply of oxygen cylinders or frequent trips to a recharging station to replenish the oxygen.
Another source of enriched oxygen is a metal cylinder storing liquid oxygen. This is in many ways similar to the storing of oxygen gas under high pressure. However, the liquid oxygen storage does not present the dangers associated with the high pressure of storing the oxygen gas. Nevertheless, the liquid oxygen is hazardous because it must be kept at an extremely low temperature, which will cause severe burns to the skin if the liquid oxygen contacts a person's skin. Again, sufficient oxygen must be kept on hand to supply the user between times when the storage cylinders can be refilled.
Systems for taking room air, which is 21% oxygen, and concentrating the oxygen to obtain a much higher percentage of oxygen are useful in that they do not require the refilling of oxygen cylinders, and can supply a virtually continuous flow of oxygen. However, the plumbing of these continuous supply systems is typically complicated and subject to leaks, and requires a large amount of power to drive the gasses through the system. These systems therefore generally use components that require a 110 volt AC power source, making these systems large and heavy. Thus, these systems are not portable, and the user is limited in his mobility if he needs frequent or continuous oxygen supply.